Recent work with both avian and mammalian infants has demonstrated that the sequential onset of functioning of the various sensory systems during prenatal development can serve as an important source of perceptual organization during the perinatal period. For example, evidence derived from precocial avian embryos and hatchlings indicates that unusually early (prenatal) visual experience can alter the normal functioning of both the auditory and visual systems during the postnatal period. However, the processes and mechanisms underlying this dynamic nature of early perceptual organization and the specific intramodal and intermodal consequences of such premature visual experience has only begun to be explicitly studied. In this application, research is proposed that will further understanding of how sensory systems and their respective stimulation histories are linked and influence one another during late prenatal and early postnatal development, in order to establish how usual (or abnormal) sensory experiences serve to maintain, facilitate, or interfere with the usual course of perinatal intersensory development. Related studies, utilizing precocial avian embryos and hatchlings, will employ an "early exposure" design to examine: (1) what experiential factors determine whether modified sensory stimulation facilities or interferes with intrasensory and intersensory development, (2) the nature of the relationship between amount, type, and modality of sensory stimulation during the perinatal period, (3) the roles of embryonic attention and behavioral arousal in the development of early perceptual organization, and (4) how transient or long-lasting are the effects of modified prenatal sensory stimulation for precocial infants. The integration of research findings from the animal literature and the human infant literature will be facilitated through extensive directed readings and collaborations and interactions with experts in each field. The candidate will also organize and participate in specialized conferences and seminars, train graduate students, and contribute to the empirical and theoretical developmental literature concerned with intersensory integration.